Swift confusing generic types

gistfile1.txt

class Cell: UITableViewCell {
    
    func hello() -> String {
        return "hello"
    }
    
}

var payload = [Int: AnyObject]()
payload[1] = Cell()
payload[2] = UITableViewCell()

func cellForKey<T: UITableViewCell>(key: Int) -> T? {
    return payload[key] as? T
}

let cell1: Cell? = cellForKey(1) // Is of type Cell, works fine
cell1?.hello()

let cell2: Cell? = cellForKey(2) // Is of type UITableViewCell instead of .None
cell2?.hello() // crashes